At present, platelet aggregation inhibitors such as aspirin have been found to be clinically effective. However, there is a continuing desire for the development of new platelet aggregation inhibitors paricularly those having certain additional effects.
It has been known that a compound of the formula 1-(2-diethylaminoethyl)-3-(p-methoxybenzyl)-1,2,-dihydroquinoxaline-2-one (hereinafter referred to as "caroverine") fumarate (this salt is hereinafter referred to as "caroverine fumarate".) increases blood flow by dilating arterial vessels, and that it has a spasmolytic effect (cr. Japanese Patent Laid-open (KOKAI) No. 160417/1975, etc.).
Caroverine fumarate is a known compound and is produced, for example, by a process which is described in the said Japanese Patent Application Laid-open. ##STR1##